The deposition of silicon epitaxial layers on silicon and other substrates/surfaces, such as sapphire and gallium arsenide, is a basic processing step in the fabrication of integrated circuits. Typically, homoepitaxial films of silicon are grown using silane dichlorosilane, (SiH.sub.2 Cl.sub.2), trichlorosilane (SiHCl.sub.3), or silicon tetrachloride (SiCl.sub.4) in the temperature range of 1000.degree.-1200.degree. C. Low-temperature growth has recently drawn increased attention due to the superior control of film thickness and dopant redistribution, particularly in the fabrication of submicron geometry devices.
Laser-induced chemical vapor deposition (LCVD), reduced pressure CVD, plasma enhanced CVD (PECVD), molecular beam epitaxy (MBE), and ultrahigh vacuum CVD (UHVCVD have been investigated as alternatives to conventional silicon epitaxial techniques. An additional advantage of the low-temperature growth techniques such as ultra high vacuum CVD and MBE is the controlled growth of abrupt thin layers of high quality silicon.
There has remained a need to develop a simple but effective relatively low temperature process which is adapted to industrial use and which enables convenient doping during deposition of the silicon onto the substrate. It is also desirable to provide a continuous process using a reactor which permits removal and insertion of reactants and removal of product as the process continues.
It is an object of the present invention to provide a novel, continuous flow relatively low temperature process for depositing epitxial layers of silicon and silicon alloys upon substrates, in which the process is readily adapted to industrial use.
It is also an object to provide such a process which is adapted to the deposition of silicon-germanium alloys.
Another object is to provide such a process which enables facile in situ doping of the film as it is being deposited, and facile introduction and removal of materials during the continuing process.